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H2020

MINOTOR Report Summary

Project ID: 730028

Periodic Reporting for period 1 - MINOTOR (MagnetIc NOzzle thruster with elecTron cyclOtron Resonance)

Reporting period: 2017-01-01 to 2017-12-31

Summary of the context and overall objectives of the project

The MINOTOR project’s (MagnetIc NOzzle elecTron cyclOtron Resonance thruster) main objective is to demonstrate the feasibility of the ECRA technology (Electron Cyclotron Resonance Accelerator) as a disruptive technology for electric propulsion, and to prepare roadmaps for the potential future developments of the technology. The project is focused on the understanding of the physics and the demonstration of the technology, rather than on the production of a fully operational prototype.

Based on electron cyclotron resonance (ECR) as the sole ionization and acceleration process, ECRA is a cathodeless thruster with magnetic nozzle, allowing thrust vectoring. It has significant potential advantages in terms of global system cost and reliability compared to mature technologies. It is also scalable and can potentially be considered for all electric propulsion applications.

The plasma is created by ECR inside the thruster cavity by injecting and ionizing neutral gas, resulting in a high-density plasma. The topology of the external magnetic field is purely diverging and acts as a magnetic nozzle, where the magnetized electrons are accelerated by the conservation of the electron energy and magnetic moment µ. This leads to an ambipolar electric field that directly accelerates ions to high velocities. Electrons with high energy escape the potential barrier to conserve the quasi-neutrality of the exhaust plasma beam, which is ensured since the thruster is floating. Thus, neither grids nor hollow cathode neutralizers is not needed. The plasma then detaches from the magnetic lines and produces a net thrust force.

The first results obtained with ECRA have been encouraging, but the complexity of the physics at play has been an obstacle for the understanding and development of the technology. Indeed, the ionization chamber involves absorption of microwave energy in a magnetized, flowing plasma, which is challenging to model, and the understanding of the physics in the magnetic nozzle is still a subject of research. Thus, an in-depth numerical and experimental investigation plan has been devised for the project, in order to bring the ECRA technology from TRL3 to TRL4.

In order to demonstrate the potential of this technology in comparison to other technologies in a large range of thrust levels, it is planned to have achieved the following objectives by the end of the project:
• Get a full understanding of the physics, by in-depth numerical modelling studies in parallel to an extensive experimental investigation, leading to optimised designs, performance maps and scaling laws for the thruster;
• demonstrate ECRA performances with tests at three thrust levels (30W, 200W and 1 kW) and erosion tests;
• demonstrate features such as compatibility with alternative propellants and magnetic beam steering;
• demonstrate the feasibility of an efficient PPU;
• determine quantitatively the impact of the ECRA technology on the EP system and satellite platform at systems level, and establish the future industrial roadmaps for development. These roadmaps shall aim at realising a high TRL in the timeframe of 2023-2024.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

In the first year of the project, the following main achievements are reported:

WP1: Ethics requirements
Ethical issues were tracked but currently nothing to declare.

WP2: Project Management, Dissemination, Exploitation
• Project monitoring, tools and control, organised regular meetings and minutes.
• Delivery of internal and contractual deliverables and milestones.
• Risk Management and register.
• Regular communication with the PO and PSA.
• Produced MINOTOR project corporate identity, communication tools and dissemination: 8 papers at the IEPC (International Electric Propulsion Conference), Atlanta, 10/2017; 1 invited lecture at the EPIC workshop (Madrid, 10/2017); 2 journal articles have been submitted for publication.

WP3: Modelling
• A code development methodology has been defined for all codes of the project, based on robust code versioning and a test-driven approach.
• A literature review of ECRH, numerical schemes for plasma-wave problems, and associated issues, was carried out.
• SURFET and ROSEPIC codes are well under development, with advances in all of them in line with the planned work programme.
• The first parametric analyses have been carried out under task 3.3, with preliminary results.

WP4: Thruster Design Optimization
• Numerous configurations of the thruster have been designed, built and tested. Trends of performances have been deduced. The results will serve to validate the models when they will be available.
• In-vacuum diagnostic techniques having developed, some of them unique to this thruster technology. They have been used to gain insight into the physics of the thruster.
• Several performance figures (thrust, efficiency, electromagnetic emission) have been assessed.
• In order to remove the antenna, a waveguide version of the thruster has been computed and designed.

WP5: Alternative Propellant
This WP activities are not yet started. It is planned to start in M15.

WP6: Scale up and Erosion
• The work carried out in this first year is mostly the preparation of the Jumbo facility for the future test of high power versions of ECRA.

WP7: High Efficiency Microwave Generator
• Determination of the GAN transistor to be used.
• First study of the model of the transistor to compare with the datasheet given by the constructor (S parameters).
• Determination of the number of harmonics for the input and output to have the best performances given by the specification.
• Realization of the network matching (input and output) with lumped components.
• Determination of the substrate.
• Preliminary assessment of calculated performance of the amplifier and combiner structure.

WP8: System impact
• Analysis of the needs of the ECR technology.
• Assessment of the impact of the ECR thruster on the PPU architecture.
• Assessment of the relative cost saving of ECR technology on the PPU.

WP9: System impact
• A set of reference thruster performances has been gathered to compare to ECRA.
• The performance of ECRA is regularly monitored to assess potential progress.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

All the achievements presented in the previous section represent and advancement with respect to the state of the art on ECR thruster.

The main outcomes to be derived from MINOTOR are the following:
• Provide a cost effective alternative to current technologies.
• Leverage effect and benefit for EU partners.
• Mass adoption of the technologies.
• Market penetration.

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